Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Compact heat-generating devices, such as integrated-circuits (including microprocessors, graphics chips, radio frequency (RF) chips, networking communication chips, microwave chips, etc.), laser diodes, light-emitting diodes (LEDs), vertical-cavity surface emitting lasers (VCSELs), batteries, electronic modules, optical modules, electro-optical modules, RF modules, electro-chemical modules, mechanical modules and the like, generate thermal energy, or heat, when in operation. Compact heat-generating devices may function as, for example, sensors or ASIC drivers in a telecom router, cellular phone tower, data communications server or mainframe computers. Regardless of which type of heat-generating device the case may be, heat generated by a compact heat-generating device needs to be removed or dissipated from the compact heat-generating device in order to achieve optimum performance of the compact heat-generating device by keeping its temperature within a safe operating range. With the form factor of compact heat-generating devices and the applications they are implemented in becoming ever smaller (e.g., the processor in a smartphone, a tablet computer or a notebook computer) and thus resulting in high heat density, it is imperative to effectively dissipate the high-density heat generated in an area of a small footprint to ensure safe and optimum operation of compact heat-generating devices operating under such conditions.
Many metal-based water-cooled and air-cooled cooling packages have been developed for use in compact packages to dissipate heat generated by the various types of compact heat-generating devices mentioned above. For instance, heat exchangers and heat pipes made of a metallic material with high thermal conductivity, such as copper, silver, aluminum or iron, are commercially available. However, most metal-based heat exchangers and heat pipes experience issues of oxidation, corrosion and/or crystallization after long periods of operation. Such fouling factors significantly reduce the heat transfer efficiency of metal-based heat exchangers and heat pipes. Other problems associated with the use of metal-based cooling packages include, for example, issues with overall compactness of the package, corrosion of the metallic material in water-cooled applications, difficulty in manufacturing, and so on. With increasing demand for high power density in small form factor, there is a need for a compact cooling package for compact heat-generating devices with fewer or none of the aforementioned issues.
One issue with heat dissipation in portable/mobile applications is that, even when heat generated by a compact heat-generating device (e.g., the processor in a smartphone, a tablet computer or a notebook computer) is removed or otherwise transferred away from the compact heat-generating device itself, this thermal energy is transferred to other portions of a portable/mobile electronics apparatus in which the compact heat-generating device is enclosed. This may be undesirable especially in portable/mobile applications. For instance, at least a portion of the heat generated by a microprocessor in a smartphone or tablet computer is transferred to the enclosure of the smartphone or tablet computer (e.g., a portion of the apparatus's enclosure closest to the microprocessor), thus making at least a portion of the enclosure warm or even hot to touch. As another example, some notebook computers may have a cooling fan installed therein to promote heat transfer by convection to cool off the microprocessor of the notebook computer. Still, warm air can be felt near a vent of the enclosure where the cooling fan blows hot air out of the enclosure, and at least a portion of the enclosure of the notebook computer may still be warm or even hot to touch. Consequently, user experience of such portable/mobile electronics apparatus may be negatively impacted if not rendered harmful.